Biometric sensors such as fingerprint sensors are becoming increasingly common in a wide range of applications such as computers, smartphones, smartcards and other applications where biometric identity verification is required. In particular, capacitive fingerprint sensors have been shown to provide accurate performance while being cost efficient and suitable for large scale manufacturing.
While fingerprint sensors often are manufactured in very large volumes with high manufacturing accuracy and high yield, it may still be desirable to test the produced sensors, thereby requiring efficient and automated test procedures. Moreover, when testing the sensors it is desirable to perform testing using a test structure which is as similar to a human finger as possible in order to replicate normal operating conditions for the sensor.
In particular, it is desirable to test the fingerprint sensor so that it is working as expected and that it captures images of sufficiently high quality. Since it is not practical to test the fingerprint sensor with an actual finger, a test rig can be used which comprises a rubber stamp or a rubber probe having a pattern allowing the functionality of the fingerprint sensor to be verified.
US2015/0070037 discloses a probe apparatus for testing a fingerprint sensing device where the device to be tested is located with a video camera, the probe is aligned with the device to be tested and the probe is lowered towards the sensor to contact the target. The probe apparatus comprises a housing in which the probe is mounted e.g. via a gimbal structure to allow the probe to move to adapt to misalignment of the contact surface.